As transmission line protective relay devices, there are available for example current differential relay devices or directional comparative distance relay devices. Of these, a current differential relay device distinguishes and detects with high accuracy internal faults or external faults in zones that are to be protected, by employing the current of the transmission line terminals. Typically, distinguishing between internal faults and external faults is performed by finding the vector sum of the terminal currents as the operating amount (Id) and finding the scalar sum of the terminal currents as the suppression amount (Ir); ratio/difference characteristics are constructed using this operating amount (Id) and suppression amount (Ir) and operation or non-operation are distinguished in terms of these characteristics.
FIG. 18 shows an example of the layout of a current differential relay device and the typical ratio difference characteristic. FIG. 18 shows a current differential relay device Ry-A that is arranged at one terminal (terminal A) of a transmission line TL of two-terminal construction. CTA and CTB are respectively instrument current transformers arranged at the terminal A and terminal B; 2 is input processing means; 3 is reception processing means; and 11 is computation means. The computation means 11 comprises: a vector sum computation section 11−1 that calculates the vector sum (Id) of the transmission line currents IA, IB; a scalar sum computation section 11−2 that calculates the scalar sum (Ir) thereof; and an operation evaluation section (OES) 11−3 of the ratio difference characteristic (RDC). Even in the case of a system with three or more terminals, the operating amount Id is also found by the vector sum of the totality of terminal currents and the suppression amount Ir is also found by the scalar sum of the totality of terminal currents.
The operation evaluation section 11−3 using the ratio difference characteristic shown in FIG. 18 employs two characteristics, namely: a small current zone characteristic (Df1) that is arranged to be capable of detection even when the fault current is small, as in the case of an internal fault; and a large current zone characteristic (Df2) for preventing spurious operation from being produced by the difference in error currents amplified by the instrument current transformer CT when large current passes, as in the case of an external fault: when Df1 and Df2 are both operating, the current differential relay device that is thereby constituted generates an operating output.
FIG. 19 shows the case where a current differential relay device is applied to a transmission line of three-terminal construction. When this transmission line relay protective device is applied to a three-terminal transmission line, as shown in FIG. 19, occurrence of a fault in the zone that is subject to protection is diagnosed by finding the operating amount and suppression amount in the same way as in the case of a two-terminal transmission line as described above, but using the current information of this three-terminal transmission line: the current information of a terminal in question is delivered to the two remote terminals through the transmission line or the respective local current information is acquired through the transmission line simultaneously from the two remote terminals. Lab, Lbc, Lca, indicated by the broken lines, are communication channels arranged between the current differential relay devices of each terminal: specifically, the communication channel Lab connects the current differential relay device Ry-A of the terminal A and the current differential relay device Ry-B of the terminal B; the communication channel Lbc connects the current differential relay device Ry-B of the terminal B and the current differential relay device Ry-C of the terminal C; and the communication channel Lca connects the current differential relay device Ry-C of the terminal C and the current differential relay device Ry-A of the terminal A. Although these communication channels are indicated in the drawings by wires, they could of course be constituted by exchange of electromagnetic waves.
FIG. 20 shows the case where a current differential relay device is applied to a transmission line of five-terminal construction.
Although, in the case of transmission lines of a construction with four terminals or more, the communication channel layout has a star configuration, the principle is the same as in the case of a transmission line of two-terminal construction, except for the fact that the number of data-sending parties and the number of data-receiving parties are different.
Next, the case of a directional comparative distance relay device will be described. In the case of the directional comparative distance relay device, the fault direction and the distance to the fault point with reference to the installation position of the relay device are found from the voltage and current relationship detected at each terminal of the transmission line. There are a number of ways of doing this: FIG. 21 shows the characteristic of a directional distance relay, called a Mho type relay. In the case of a Mho type relay, it operates when there is the impedance found from the voltage and current in the circular region of the Mho characteristic.
FIG. 22 shows the case where a directional comparative distance relay device is applied to a transmission line of three-terminal construction. In this case, as a typical example, the direction evaluation operating zone of a directional comparative distance relay device Ry-A installed at the A terminal is indicated by a broken line. The reason why the direction evaluation operating zone is extended as far as and including the region to the rear of terminal B and terminal C is in order to find fault points in the region from the terminal A to beyond the remote terminals (terminal B, terminal C): this is called overreaching. When the directional comparative distance relay device of any terminal is operated, the information is transmitted to the remote terminals. At each terminal, if the information at the terminal in question and the incoming information from two remote terminals (in the three-terminal case) all indicate a forward fault, the fault point is evaluated as being internal, and the breakers at each terminal are tripped.
In the case of FIG. 22, if the directional comparative distance relay device Ry-A installed at terminal A indicates a forward fault, and signals indicating detection of a forward fault are received from the directional comparative distance relay device Ry-B of the terminal B and the directional comparative distance relay device Ry-C of the terminal C, terminal B and terminal C being remote terminals, finally, a trip signal is sent to the breaker of the terminal in question (the terminal A). Exactly the same applies in the case of the directional comparative distance relay device Ry-b installed at the terminal B and the directional comparative distance relay device Ry-C installed at the terminal C.
Other examples of a directional comparative distance relay device include a system in which a block signal (breaker trip blocking signal) is sent to a remote terminal if a rearward fault is found, or a breaker trip-enabling signal is sent to a remote terminal when an internal fault is detected, or combinations of such systems. Although the logic of the fault evaluation section differs, depending on the system, they have in common a device or communication channel whereby signals are exchanged with remote terminals.
And, in order to improve reliability of the transmission line protective relay device, various inventions have been disclosed in which the transmission means that transmits the terminal information is duplicated.
Examples of such devices are disclosed in laid-open Japanese Patent Application No. Tokkai H 11-69606 (hereinafter referred to as Patent Reference 1), Tokkai H 10-23654 (hereinafter referred to as Patent Reference 2) and Tokkai 2007-236097 (hereinafter referred to as Patent Reference 3).
With the invention set out in Patent Reference 1, if some problem occurs on a communication channel in a transmission line protective device with three or more terminals, an attempt is made to deliver the signal by reconstituting the communication channel; however, there was the problem that, since the method of communication was altered after detection of occurrence of a communication malfunction, arrival of the information with the remote party was delayed. Also, processing tends to become complicated due to the need to achieve urgent processing.
Also, the invention set out in Patent Reference 2 consists in a multi-terminal transmission line protective relay device in which two or more terminals comprise a parent device and the remaining terminals comprise a child device; in this system, when the protective relay of the parent device detects occurrence of a fault, a trip command is delivered to the protective relay of the child devices. In the case of this system, while there is the advantage that the computation can be performed once information has been collected by some of the protective relays, there is the problem that, owing to the need to deliver the computation result of the protective relay to the other devices, operation is delayed to that extent. Also, since a trip command is delivered, if for example a trip command is output by mistake due to the occurrence of some problem in the protective relay that performs the calculation, there is a risk that all the other protective relays will be tripped.
Furthermore, although, in the case of the invention set out in Patent Reference 3, reliability is increased by the fact that all transmissions are duplicated, this has the problem of increasing costs.
Accordingly, an object of the present invention is to provide a transmission line protective relay device installed on a transmission line of three or more terminals wherein equipment costs can be suppressed and even if a partial communication failure occurs, recovery can be achieved in a comparatively short time, by having each terminal transmit the incoming terminal information transmitted from other remote terminals in combined fashion when information of the terminal in question is transmitted to a predetermined remote terminal.
In order to achieve the above object, a transmission line protective relay device according to Embodiment 1 is constructed as follows. Specifically, a transmission line protective relay device wherein evaluation of whether or not a fault has occurred on a protected transmission line that has terminals with transformers installed on multiple transmission lines with three terminals or more is performed by mutual exchange of terminal information based on the currents input from the transformers of each terminal through respective communication channels, and current difference computation is performed using the terminal information of the terminal in question and the incoming terminal information received from remote terminals respectively comprises:
an input processing means that is arranged to connect the transmission line protective relay device arranged at each terminal with each communication channel, and to output the incoming current at the terminal in question as terminal information by input processing, at each transmission line protective relay device of each terminal;
a plurality of reception processing means that respectively receives terminal information delivered from a remote terminal connected with the terminal in question by a communication channel;
a computational processing means that performs current difference computation by inputting the terminal information that was output from said input means and the terminal information of the remote terminal that was output from said plurality of reception means; and
a transmission processing means that transmits main terminal information constituting the terminal information of the terminal in question and backup terminal information constituting terminal information of a remote terminal that is different from the remote terminal in question, to a remote terminal connected by a communication channel with the terminal in question;
and is characterized in that said computational processing means, if main terminal information and backup terminal information cannot be received in a predetermined time from an arbitrary communication channel of the communication channels, performs current difference computation using the terminal information of all of the terminals, using the backup terminal information delivered through another communication channel, instead of the main terminal information that could not be received from the communication channel in question.
Also, a transmission line protective relay device according to Embodiment 2 is constructed as follows. Specifically, a transmission line protective relay device wherein evaluation of whether or not a fault has occurred on a protected transmission line that has terminals with transformers installed on a transmission line with three terminals or more is performed by mutual exchange of terminal information relating to the calculated direction of the fault point and impedance as far as and including the fault point based on the voltages and currents input from the transformers of each terminal through respective communication channels, from the information of the terminal in question and the terminal information delivered from a plurality of remote terminals respectively comprises:
an input processing means that is arranged to connect the transmission line protective relay device arranged at each terminal with each communication channel, and to output the voltage and current that are input from the transformer at the terminal in question as terminal information by input processing, at each transmission line protective relay device of each terminal;
a plurality of reception processing means that respectively receives terminal information delivered from a remote terminal connected with the terminal in question by a communication channel;
a computational processing means that determines whether a forward fault is present or not by calculating the direction of the fault point and the impedance as far as and including the fault point, based on the voltage and current of the terminal in question that are output from said input processing means;
a final decision section that inputs the computation result data obtained by said computational processing means and the terminal information that is output from said plurality of reception processing means and that makes a final decision to identify a transmission line as faulty, if all of this terminal information identifies this as a forward fault; and
a transmission processing means that transmits main terminal information constituting the calculation results data of the terminal in question and backup terminal information constituting terminal information of a remote terminal that is different from the remote terminal in question, to a remote terminal connected by a communication channel with the terminal in question;
and is characterized in that said final decision section, if main terminal information and backup terminal information cannot be received in a predetermined time from an arbitrary communication channel of the communication channels, makes a final decision using the backup terminal information delivered through another communication channel, instead of the main terminal information that could not be received from the communication channel in question.
Further, a transmission line protective relay device according to embodiment 5 wherein evaluation of whether or not a fault has occurred on a protected transmission line wherein respective transmission line protective relay devices are installed at both terminals of a two-terminal transmission line that has two circuits installed, terminal information being exchanged through communication channels mutually between the transmission line protective relay devices that are respectively provided on opposite terminals, using the terminal information of the terminal in question and the terminal information received by a remote terminal is characterized in that it comprises:
an input processing means that delivers output as information of the terminal in question by input processing of the current that is input from the transformer of the terminal in question;
a first reception processing means that receives the terminal information transmitted from a remote terminal of the transmission line that is being protected;
a second reception processing means that receives terminal information transmitted from one terminal of a transmission line that is not being protected;
a third reception processing means that receives data obtained by said remote terminal of said transmission line that is being protected, in addition to the terminal information obtained by the other terminal of said transmission line that is not being protected;
a first transmission processing means that transmits to a remote terminal of said transmission line that is being protected the terminal information of the terminal in question that was output from said input means;
a second transmission processing means that transmits in combination to a transmission line protective relay device provided at another terminal of said transmission line that is not being protected, the terminal information that is output from said second reception processing means and the terminal information of the terminal in question that is output from said input means;
a third transmission processing means that transmits terminal information obtained by the other terminal of the transmission line that is not being protected, of the terminal information output from said third reception processing means, to a transmission line protection relay device of said one terminal of this transmission line that is not being protected; and
a computational processing means that performs protective computation by inputting terminal information obtained by the other terminal of the transmission line, which is being protected, of the terminal information of the terminal in question that was output from said input means and the terminal information that was output from said first reception processing means and the terminal information that was output from said third reception processing means.
In addition, a transmission line protective relay device according to Embodiment 6 has the following construction. Specifically,
a transmission line protective relay device wherein evaluation of whether or not a fault has occurred on a protected transmission line wherein respective transmission line protective relay devices are installed at both terminals of a two-terminal transmission line that has two circuits installed, terminal information relating to the calculated direction of the fault point and impedance as far as and including the fault point based on the voltages and currents input from the transformers of each terminal being exchanged through communication channels mutually between said transmission line protective relay devices, by using the terminal information of the terminal in question and terminal information of a remote terminal that has thus been received, comprises:
an input processing means that delivers output as information of the terminal in question by input processing of the voltage and current of the terminal in question that is input from the transformer of the terminal in question;
a first reception processing means that receives the terminal information transmitted from a remote terminal of the transmission line that is being protected; a second reception processing means that receives terminal information transmitted from one terminal of a transmission line that is not being protected;
a third reception processing means that receives terminal information obtained by said remote terminal of said transmission line that is being protected, in addition to the terminal information obtained by the other terminal of said transmission line that is not being protected;
a computational processing means that determines whether a forward fault is present or not by calculating the direction of the fault point and the impedance as far as and including the fault point, based on the voltage and current of the terminal in question that are output from said input processing means;
a first transmission processing means that transmits to a remote terminal of said transmission line that is being protected the terminal information of the terminal in question that was output from said computational processing means;
a second transmission processing means that transmits in combination to a transmission line protective relay device provided at another terminal of said transmission line that is not being protected, the terminal information that is output from said second reception processing means and the terminal information of the terminal in question that is output from said computational processing means;
a third transmission processing means that transmits terminal information obtained by the other terminal of the transmission line that is not being protected, of the terminal information output from said third reception processing means, to a transmission line protection relay device of said one terminal of this transmission line that is not being protected; and
a computational processing means that performs protective computation by inputting terminal information obtained by the other terminal of the transmission line, which is being protected, of the terminal information of the terminal in question that was output from said input means and the terminal information that was output from said first reception processing means and the terminal information that was output from said third reception processing means.